Ultrasound Acoustic Guitar Amps
Mastering the art of keeping it natural
By Dan Semple

Ultrasound AmpsAmplifying an acoustic guitar is no piece of cake, and though there are now numerous amplifiers and pickup systems designed for amplifying acoustic guitars, most are imperfect solutions. It's usually a matter of "the operation was a success but the patient died." They can make an acoustic guitar louder, but often lose its natural, unamplified acoustic qualities in the process.

This is what I found when I began looking for a convenient, portable amp I could pack and set up easily at my solo gigs, many of which are in pubs and coffeehouses where there are noisy crowds and no house PA systems. I tried out combo after combo--from all the big name manufacturers--only to find that the rich, natural sound of the guitar I love was lost in its translation to the electrical realm. Essentially, they turned my acoustic sound into harsh, quacky electric tone, blurring the subtleties of its vibrating-wood quality.

Then I found Ultrasound

I had about given up on the idea of a convenient combo that would amplify both my guitar and my voice, when a friend suggested I try Ultrasound. He pointed out that Ultrasound specializes in acoustic guitar amps, and doesn't simply adapt electric guitar amp technologies. When I got a chance to try out two Ultrasound amps (an AG-30 and AG50) I was immediately impressed by what I heard. Both combos had the transparent sound I was seeking. They made my guitar louder without changing the acoustic character of its sound. It was the sound you get by miking a guitar and running it through a good, clean PA system. I chose the AG-50DS2 which had more power and two channels rather than just one since I needed to amplify my voice as well as my guitar.

I have been using it for over a year now, and it has proven itself an excellent combo--very compact, sturdy, and good looking--and it delivers full-range sound from its pair of 8" coaxial speakers. I was perfectly content with it until now.  Ultrasound has found ways to improve the amp I thought of as perfect. The AG-50DS4 is here.

New and improved

I actually tested two new Ultrasound models: the improved version of my AG50 and the entirely-new CP-100. The AG-50DS4 is much the same as my AG-50DS2 but it's improved in meaningful ways. The power and speakers remain the same--50W into two coaxial 8" full-range speakers-- but the front-end has been tweaked to flatten response curve for even more transparency. Also, the tendency to brittle piezo-generated trebles is softened even more.

On the rare occasions I play a larger venue, my DS2 serves me well as a stage monitor and house system feed, but the DS4 goes a step further with a balanced XLR direct out. Other improvements add even more flexibility. It has the same block of 16 digital effects as the DS2, but on the DS2 they can be used only on the instrument channel whereas on the DS4 they are assignable to either channel or both, and a footswitch jack is provided for turning them on or off. Another nifty change is the addition of combo XLR/1/4" inputs on both channels, making each usable for either instrument or microphone.

The notch filter seems the same and is quite effective. You can switch it on or off and it provides 18dB of sweepable cut. There's also a shape switch that gives you a quick way to notch the mids or make an overall adjustment for a guitar that is especially middy. The DS3 has both mono and stereo line outs, and adds a balanced XLR direct out as mentioned earlier. All these changes in the AG-50DS4 are logical and make a great amp even greater.

The CP-100

This new Ultrasound model fits squarely into the hierarchy of AG models despite its different name. It has all the features of the AG-50DS4 except for stereo line out, but adds RCA inputs for jamming along with a CD player or drum machine and for pumping out recorded music on breaks. The CP-100 also has phantom power for the XLR inputs giving you the option of using a condenser mic.

What the CP-100 really brings to the table is more power. It raises the output to 100 watts, and uses a single 8" woofer with a horn tweeter instead of two coaxials, perhaps for power handling reasons. Whatever the reason, the CP-100 has more volume and seems to throw the sound further.

What is especially remarkable, considering all of its power, is its size. The CP-100 is remarkably compact for the amount of sound it puts out: 12" high, 16" wide, and 11" deep. I haven't seen any specs on the speaker but judging from how much sound it cranks out, it has to be a very good one. It seems to handle the dual load of voice and guitar effortlessly, and I tried it at very high volume to see if it distorted at higher levels. It didn't because, as I later found, there's a built-in limiter that keeps it from being overdriven.

I didn't think I'd be yearning for a new amp so soon after getting my AG-50DS2, but already I'm deciding between the new AG-50DS4 and the CP-100. Good work, ork, Ultrasound.